A Conceptual Framework For Cosmology

[jedaisoul]

Synopsis

 

A thought experiment is used to investigate the effects of the invariance of the velocity of light in a Newtonian environment. This reveals an apparent inconsistency, in that two observers can receive different time signals from a distant transmitter, even though they are adjacent at that moment. The inconsistency is resolved by adopting a novel conceptual framework, a simultaneity-time continuum, in which the physical relationships between macroscopic objects remain Newtonian but the observed relationships can, and will, differ.

 

 

Introduction

 

Galilean Invariance (which is also referred to as Newtonian Relativity) is a form of relativity that was originated by Galileo. In this scenario:

• The relationships between frames of reference is defined by the Galilean Transformation (as opposed to the Lorentz Transformation of Special Relativity).
  
• There is no time dilation nor spatial contraction.
  
• The existence of a physical space in which material objects exist is presumed.

I would direct anyone who is not familiar with this form of relativity to Wikipedia, which contains an article called “Galilean Invariance”.

 

Special Relativity is regarded as a more accurate description of the behaviour of objects moving at near-light velocities, but Newtonian Relativity is sufficiently accurate for most practical purposes, and is easier to use. However, Newtonian Relativity pre-dated the discovery that the velocity of light is unaffected by the relative motion of the source and receiver. I therefore decided to use a thought experiment to examine the effects the invariance of the velocity of light would have in a Newtonian environment. I.e. if you do not introduce the concepts of time dilation and spatial contraction of Special Relativity.

 

 

A Thought Experiment on Newtonian Relativity

 

In a region of space far away from other material objects there is a radio transmitter and two girls, Alice and Betty. The transmitter emits four time signals per second. Each girl has a device capable of displaying the time signals as they are received. At 10:00:00am the transmitter sends the time “10:00:00.00”. Alice and Betty have synchronised clocks co-located with them, but as there is no time dilation in this scenario, they always indicate the same time as the transmitter.

 

Alice is at rest with respect to the transmitter and 4 light seconds distant from it. So the time displayed on her device is always 4 seconds behind the actual time (as displayed on her clock). I.e. At 10:00:00 her device displays “09:59:56.00”. At 10:00:04 her device will display “10:00:00.00”, at 10:00:05 it will display “10:00:01.00”, and so on…

10:00:00.00_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _<-Betty
Transmitter_ _ _ _ _ _ _ _ _ _ _ _ _ _ _Alice "09:59:56.00"
0_ _ _ _ _1_ _ _ _ _2_ _ _ _ _3_ _ _ _ _4_ _ _ _ _5 l sec

At 10:00:00 Betty is 5 light seconds distant from the transmitter and approaching it at 0.2c. So in 5 seconds time (at 10:00:05) she will have travelled 1 light second and be adjacent to Alice. You might therefore expect that at 10:00:05 she too would receive the time signal “10:00:01.00”. However, Betty's observations require a little more thought. In her rest frame of reference, she is stationary and the transmitter is approaching her at 0.2c. At 10:00:00, when it is 5 light seconds distant from her, the transmitter emits the time signal "10:00:00.00" and continues on its way. The time signal approaches her at the velocity of light, so Betty will receive the time signal “10:00:00.00” at 10:00:05.

10:00:05.00_ _ _ _ _ _ _ _ _ _ _ _ _ _<-Betty "10:00:00.00"
Transmitter_ _ _ _ _ _ _ _ _ _ _ _ _ _ _Alice "10:00:01.00"
0_ _ _ _ _1_ _ _ _ _2_ _ _ _ _3_ _ _ _ _4_ _ _ _ _5 l sec

So at 10:00:05, even though they are adjacent, Alice (stationary in the frame of reference of the transmitter) receives the time signal "10:00:01.00" and Betty (stationary in her own rest frame) receives the time signal "10:00:00.00". Furthermore, Betty, will see Alice’s device displaying “10:00:01.00”, and Alice will see Betty’s device displaying “10:00:00.00”. Also, as five seconds have passed since the time signal “10:00:00.00” was transmitted, both their clocks will display “10:00:05.00”. So there is no discrepancy in how much time has actually passed for Alice and Betty (as indicated by their clocks), but the time signals received on adjacent devices from a distant transmitter are out of sync.

 

At this point you may be thinking “that cannot be”. If we imagine light as a particle or wave travelling through space, then when the girls are adjacent, they should receive the same time signal. We will come back to that. For the moment, we will re-run the experiment, starting again at 10:00:00. This time, moments before they are adjacent, both girls step sideways such that at 10:00:05 each is at the exact position occupied by the other in the first experiment.

10:00:05.00_ _ _ _ _ _ _ _ _ _ _ _ _ _ _Alice "10:00:01.00"
Transmitter_ _ _ _ _ _ _ _ _ _ _ _ _ _<-Betty "10:00:00.00"
0_ _ _ _ _1_ _ _ _ _2_ _ _ _ _3_ _ _ _ _4_ _ _ _ _5 l sec

The small transverse movements should have no effect on when the girls receive the time signals, so Alice’s device will still show “10:00:01” whilst Betty’s will show “10:00:00”. The girls are at the exact positions occupied by each other in the first run, yet each still receives the time signals according to their own relationship to the transmitter.

 

Also, if we assume that the girls could see the transmitter, at 10:00:05 Alice would see it as being 4 light seconds distant, whilst Betty would see it as being 5 light seconds distant. Is there an actual difference in the distance? No. The girls see the transmitter as being at different distances because they are seeing it where it was (with respect to themselves) when the light that each receives was emitted. So even though the actual physical relationships are unaffected, the apparent relationships to a distant object can, and will, differ.

 

We can describe this effect more fully by using a sequence of “snapshots”. For brevity, I will refer to Alice, Betty and the Transmitter as A, B and T. The actual time at which each “snapshot” is taken is shown on the left. This matches the time signal emitted by the transmitter at that moment, and the times displayed on Alice and Betty’s clocks. For clarity, Betty’s distance from the transmitter is given in brackets after the time. The time displayed on the receiving devices is shown in quotes against the respective observer.

 

If at 10:00:00.00 Betty was 5 light seconds distant from the transmitter, then 1.25 seconds earlier (at 09:59:58.75) she was 1.25 x 0.2 light seconds further away. I.e. 5.25 light seconds distant. Therefore she will receive the time signal “09:59:58.75” 5.25 seconds later, at 10:00:04. At that time (10:00:04) she is 5.25 x 0.2 light seconds nearer than at 09:59:58.75, ie. 5.25 - 1.05 = 4.2 light seconds distant from the transmitter. Whereas, at 10:00:04, Alice receives the time signal “10:00:00.00” and remains 4 light seconds distant from the transmitter.

10:00:04.00 (4.2)_ _ _ _ _ _ _ _ _ _ _ _<-B "09:59:58.75"
T_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _A "10:00:00.00"
0_ _ _ _ _1_ _ _ _ _2_ _ _ _ _3_ _ _ _ _4_ _ _ _ _5 l sec

Using this logic, we can work back to the time signal that Betty received at 10:00:00 when she was 5.0 light seconds distant. However, there is an easier way to work out the steps. Alice receives 4 time signals per second, because that is the frequency they are emitted at and she is stationary with respect to the transmitter. However, Betty, because of her relative velocity, receives 5 time signals per second. Also Betty moves 0.2 light seconds nearer the transmitter. This is a linear relationship, So we can work back second by second deducting 1 second from the time displayed by Alice’s device, and 1.25 seconds from the time displayed on Betty’s device, and adding 0.2 light seconds to her distance. Thus we determine that at 10:00:00 Betty’s device displayed “09:59:53.75” when she was 5 light seconds distant from the transmitter. The complete sequence is:

10:00:00.00 (5.0)_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _<-B "09:59:53.75"
T_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _A "09:59:56.00"
0_ _ _ _ _1_ _ _ _ _2_ _ _ _ _3_ _ _ _ _4_ _ _ _ _5 l sec

10:00:01.00 (4.8)_ _ _ _ _ _ _ _ _ _ _ _ _ _ _<-B "09:59:55.00"
T_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _A "09:59:57.00"
0_ _ _ _ _1_ _ _ _ _2_ _ _ _ _3_ _ _ _ _4_ _ _ _ _5 l sec

10:00:02.00 (4.6)_ _ _ _ _ _ _ _ _ _ _ _ _ _<-B "09:59:56.25"
T_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _A "09:59:58.00"
0_ _ _ _ _1_ _ _ _ _2_ _ _ _ _3_ _ _ _ _4_ _ _ _ _5 l sec

10:00:03.00 (4.4)_ _ _ _ _ _ _ _ _ _ _ _ _<-B "09:59:57.50"
T_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _A "09:59:59.00"
0_ _ _ _ _1_ _ _ _ _2_ _ _ _ _3_ _ _ _ _4_ _ _ _ _5 l sec

10:00:04.00 (4.2)_ _ _ _ _ _ _ _ _ _ _ _<-B "09:59:58.75"
T_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _A "10:00:00.00"
0_ _ _ _ _1_ _ _ _ _2_ _ _ _ _3_ _ _ _ _4_ _ _ _ _5 l sec

10:00:05.00 (4.0)_ _ _ _ _ _ _ _ _ _ _<-B "10:00:00.00"
T_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _A "10:00:01.00"
0_ _ _ _ _1_ _ _ _ _2_ _ _ _ _3_ _ _ _ _4_ _ _ _ _5 l sec

Similarly, we can project forwards by adding 1 second to Alice‘s display, 1.25 seconds to Betty‘s display, and deducting 0.2 light seconds from Betty’s distance from the transmitter. Thus at 10:00:09 both devices display “10:00:05.00” (the time when the girls were adjacent):

10:00:06.00 (3.8)_ _ _ _ _ _ _ _ _ _<-B "10:00:01.25"
T_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _A "10:00:02.00"
0_ _ _ _ _1_ _ _ _ _2_ _ _ _ _3_ _ _ _ _4_ _ _ _ _5 l sec

10:00:07.00 (3.6)_ _ _ _ _ _ _ _ _<-B "10:00:02.50"
T_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _A "10:00:03.00"
0_ _ _ _ _1_ _ _ _ _2_ _ _ _ _3_ _ _ _ _4_ _ _ _ _5 l sec

10:00:08.00 (3.4)_ _ _ _ _ _ _ _<-B "10:00:03.75"
T_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _A "10:00:04.00"
0_ _ _ _ _1_ _ _ _ _2_ _ _ _ _3_ _ _ _ _4_ _ _ _ _5 l sec

10:00:09.00 (3.2)_ _ _ _ _ _ _<-B "10:00:05.00"
T_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _A "10:00:05.00"
0_ _ _ _ _1_ _ _ _ _2_ _ _ _ _3_ _ _ _ _4_ _ _ _ _5 l sec

Similarly, at 10:00:25 Betty arrives at the transmitter, and her device (not surprisingly) shows “10:00:25.00”. Betty’s device shows “10:00:21.00”.

10:00:25.00 (0.0)
B "10:00:25.00"
T_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _A "10:00:21.00"
0_ _ _ _ _1_ _ _ _ _2_ _ _ _ _3_ _ _ _ _4_ _ _ _ _5 l sec

We have followed Betty’s progress over a 25 second period. The timings of her receipt of the time signals follow a consistent pattern. The only apparent illogicality is that, when the girls are adjacent, they receive different time signals. If this is correct, then we can draw an important conclusion from these results:

 

As was mentioned earlier, if space were a physical entity, these results could not arise. Light would travel at a fixed velocity with respect to space, and when the girls were adjacent they would receive the same time signal. This suggest that, in this scenario, space does not exist as a physical entity, at least, so far as light is concerned. Yet it is fundamental to Newtonian mechanics that material objects behave as if space exists physically. We will deal with this apparent contradiction in the next section…

 

Note: You may have noticed that the Doppler effect has not been mentioned. Because of her relative velocity, Betty will see the time signals as being Doppler shifted. However, that does not affect the times encoded in the signals, nor when they will be received. Therefore, the Doppler effect can be ignored for these purposes.

 

 

A Simultaneity-Time Framework for Cosmology

 

The problem identified with the invariance of the velocity of light in a Newtonian scenario is that two observers can receive different time signals from a distant transmitter, even though they are adjacent at that moment. Furthermore, when the experiment is re-run and the observers swap places, they still receive the time signals related to their own relationship to the transmitter. If you regard space as a physical entity, and light as particles or waves travelling through that space, then this is impossible. It simply could not happen.

 

So how do we resolve this? Well, if material objects behave as if space exists as a physical entity, but light behaves as if it isn’t, then it’s as if there are two different universes that interact and affect one another. I say as if because I do not mean to imply that this is actually the case. Merely that the universe appears to be different to different types of entities. Hence the nature of the actual universe (according to this scenario) must support both views.

 

I would also add as axioms that:

• The universe obeys causality.
  
• The past, present and future do not co-exist. Time is not a dimension, at least, not in the same sense that the spatial ones are.

Note: Every scientific model of the universe (that I am aware of) treats time as a dimension. This is necessary if we are to model change, cause and effect, and the way that entities interact. This does not invalidate the models, but it is important to recognise that this feature of a model may have no corollary in the actual universe.

 

Also, I propose to focus on two classes of entities:

• Massless entities that can travel at the velocity of light, and whose velocity is unaffected by the relative velocity of the source and the observer. For brevity I refer specifically to photons.
  
• Macroscopic objects that have mass, cannot travel at the velocity of light, and whose velocity is affected by the relative velocity of the source (if any) and the observer. For brevity I refer to “macro objects”.

 

So how do we put together a framework for a cosmology that meets these criteria? Well, firstly, if space does not exist as a physical entity in the universe experienced by photons, then it cannot exist in the actual universe. But if that is so, what meaning can we attribute to spatial distances, and what causes the delay between photons being emitted by one object and being received by another? It cannot be the time taken for the photon to “travel” through space from one to the other, as space does not exist to photons in this scenario.

 

We can resolve this by adapting an idea suggested by Einstein; that of differences in simultaneity. Einstein suggested that simultaneity was dependent on the frame of reference. I.e. That two events which are simultaneous when seen from one frame of reference may not be so from a different frame of reference. Lets take this idea, but instead of attributing the effect to the relative motions of the frames of reference, what if it is an inherent property of macro objects?

 

Putting this another way… Conventionally we would say that where an object is determines when it experiences events. But if space does not actually exist, what determines where an object is? So, instead, let us reverse this causal relationship and state that when an object experiences events determines where it is. Thus we may say that if there is a delay of five seconds between the emission of light by one body, and it’s reception by another, it is because there is five seconds difference in their view of when that event occurred, I.e. their view of simultaneity differs by five seconds. So we may say that those two objects are five light seconds apart, which, using c, translates into a spatial distance of one and a half million kilometres (or thereabouts).

 

Of course space is not one dimensional, it is three dimensional, and this suggests that the differences in simultaneity are three dimensional. This does not explain why space is three dimensional, it merely acknowledges that it is. Put simply, if this were not so, the universe would not be as it is. So instead of a space-time universe, we end up with a simultaneity-time universe which macro objects experience in a Newtonian manner, but photons experience in a quite different way.

 

Furthermore, this suggests that, rather than being a velocity, c is an universal constant that links a difference in simultaneity between two macro objects to the physical distance between them. Which might explain why the velocity of light and the velocities of the source and receiver do not add.

 

Thus we can reconcile the invariance of the velocity of light with Newtonian Relativity by adopting a simultaneity-time framework for cosmology.

 

This leads to the question of whether the universe might actually be a simultaneity-time continuum? How could we tell? Well, in principle, the time dilation and spatial contraction effects of Special Relativity are real (affecting the actual passage of time and spatial distances), whereas the effects of this scenario are apparent (only affecting the view of distant objects). However, the practicality of performing an experiment with macro objects to determine which scenario corresponds more closely to reality is another matter. Which is why at the moment, this is just an interesting idea. At least, I hope that, if you have read this far, you found it interesting.

[insane_alien]

so you want to base a framework on a model that is known to break down in conditions commonly experienced by the objects you want to study in the framework?

 

that doesn't work. you just get something that doesn't correspond to reality. to draw conclusions from something that starts off from a false assumption(worse, a KNOWN false assumption) will only lead to false conclusions.

 

therefore, aside from being a mildly interesting intellectual exercise in futility, is completely useless for any real application of cosmology.

[foodchain]

I don’t like the term time signals, something just does not click about it. As far as I know of course do any time signals exist non dependent on physical reality? Of course being time not fully defined physically does not help either I would suggest.

 

I mean the time evolution operator because it can describe some facet of nature then should mean this is a facet of such nature, but is that so? So the concept of quantum foam. See gravity and time seem to have something in common from what I understand, or at least they can interact. So how does any of the understanding equate of the concept of quantum foam if such is a real aspect of nature.

 

See as a biology student the one thing I have surely noticed about nature is its interaction with itself and of course what appears to be a continuity or continuum to it also. Nature seems to be some meshed entity of itself, or moreover I don’t understand how you say one part of nature is totally a separate entity to its own reality, it is after all nature.

 

So basically in physics you have so many grand ideas, I don’t think any single one is small. They are all vastly complex giving the reality of which the field studies. Also the field is fully dependent on the use of mathematics to describe and or explain this reality, which then couples even more complexity into the equation. Lastly its also a human endeavor, so just add one more error bar to everything:D

 

So basically what I am saying is for any thought experiment, you do you validate the reality of knowledge which you work with even is correct or in line with how nature actually operates?

[jedaisoul]

...therefore, aside from being a mildly interesting intellectual exercise in futility, is completely useless for any real application of cosmology.

 

Hi IA, Well thanks for bothering to read the OP, and for your forthright opinions. I agree that this is, at present, entirely useless for any real application for cosmology. That is why I put it in the "speculative" section rather than the "physics" section (knowing that it would be moved anyway!).

 

What is the purpose of having a "speculative" section of the site if it is not to speculate on things which are currently un-provable? Anyway, I’m glad that you found it mildly interesting. I thought that the idea of reversing the conceptual relationship “where you are determines when you see things” is a real corker. A genuine piece of original thinking. But then, I’m biased.

 

So you want to base a framework on a model that is known to break down in conditions commonly experienced by the objects you want to study in the framework? That doesn't work. you just get something that doesn't correspond to reality. to draw conclusions from something that starts off from a false assumption (worse, a KNOWN false assumption) will only lead to false conclusions.

 

Well so does Einsteinian Relativity, it just fails to describe the real universe in a different way. This is because General Relativity is based on the presumption that time travel is possible. That’s just silly.

 

And if you are going to say “oh no it isn’t (based on that presumption)” let me quote from Einstein’s 1916 paper, where he defined general co-variance: “So there is nothing for it but to regard all imaginable systems of co-ordinates, on principle, as equally suitable for the description of nature”. I.e. As Einstein was talking in the context of a Minkowski spacetime continuum, general co-variance, the cornerstone of GR, is based on the assumption that time travel is possible (albeit it may not be feasible).

 

On the other hand, if you are going to say “oh no it isn’t (silly)”, just consider the following:

 

The concept of time travel inherently involves atoms and molecules being in two places at the same time and/or not being in any place at another time. Example: Lets assume that I have a bowl, an apple and a time machine...

 

a) At time 1, I place the apple in the bowl. A "second" me appears and places a "second" apple in the bowl. So there are two apples in the bowl.

 

b) At time 2, I pick up the first apple from the bowl and walk away from the table. The "second" me travels to time 5. The "second" apple remains in the bowl.

 

c) At time 3, I travel back in time to time 1 with the apple in my hand, becoming the "second" me at time 1.

 

d) At time 4, Neither I nor the "original" apple are there. Only the "second" apple remains in the bowl.

 

e) At time 5, The "second" me returns. So there's only one apple and only one me again.

 

You can describe my, the apple's, and the bowl's behaviour in three different world lines, but does that make it credible? The molecules and atoms that exist at different places in space are different entities. But the molecules and atoms that exist at different times are (mostly) the same entities. That is a huge difference, and GR fails to make that distinction. Are you really telling me that GR corresponds to reality?

 

I think that, despite the many achievements of Einsteinian relativity, there is a desperate need to re-assess cosmology. That includes considering ideas that are, at present, un-provable. Also, although simultaneity-time is un-provable, it can, in theory, be disproved. If you (or anyone) can find a logical flaw in the scenario I propose, that would disprove it.

 

Anyway, thanks again for reading the OP and for offering your opinions.

[timo]

Well so does Einsteinian Relativity, it just fails to describe the real universe in a different way. This is because General Relativity is based on the presumption that time travel is possible. That’s just silly.

 

And if you are going to say “oh no it isn’t (based on that presumption)” let me quote from Einstein’s 1916 paper, where he defined general co-variance: “So there is nothing for it but to regard all imaginable systems of co-ordinates, on principle, as equally suitable for the description of nature”. I.e. As Einstein was talking in the context of a Minkowski spacetime continuum, general co-variance, the cornerstone of GR, is based on the assumption that time travel is possible (albeit it may not be feasible).

What does this quote have to do with time travel? What is time travel?

[jedaisoul]

I don’t like the term time signals, something just does not click about it. As far as I know of course do any time signals exist non dependent on physical reality? Of course being time not fully defined physically does not help either I would suggest.

 

Hi foodchain. The primary purpose of the time stamps is to provide a consistent way of labelling signals to distinguish them. This makes the point that when the girls are adjacent, they receive different signals from the remote transmitter. Exactly what those signals mean is a secondary consideration. However, as this is a Newtonian environment (in which there is no actual time dilation nor spatial contraction), I think that it is perfectly legitimate to use the time stamps to relate back to when the signals were transmitted, and where the girls were at that time. Of course, that is not so if you posit a different scenario.

 

I mean the time evolution operator because it can describe some facet of nature then should mean this is a facet of such nature, but is that so? So the concept of quantum foam. See gravity and time seem to have something in common from what I understand, or at least they can interact. So how does any of the understanding equate of the concept of quantum foam if such is a real aspect of nature.

 

Sorry, I don’t understand how this is relevant to my scenario.

 

See as a biology student the one thing I have surely noticed about nature is its interaction with itself and of course what appears to be a continuity or continuum to it also. Nature seems to be some meshed entity of itself, or moreover I don’t understand how you say one part of nature is totally a separate entity to its own reality, it is after all nature.

 

Where did I say that? The idea that all macro objects are interrelated and interact is consistent with the conclusion that space does not actually exist, and that distances are merely relationships between objects.

 

So basically in physics you have so many grand ideas, I don’t think any single one is small. They are all vastly complex giving the reality of which the field studies. Also the field is fully dependent on the use of mathematics to describe and or explain this reality, which then couples even more complexity into the equation. Lastly its also a human endeavor, so just add one more error bar to everything

 

I’m not sure what point you were making. All I can say is that mathematics is a two edged sword; it is reality neutral.

 

So basically what I am saying is for any thought experiment, you do you validate the reality of knowledge which you work with even is correct or in line with how nature actually operates?

 

I’d rephrase the question as “…for any thought experiment you do, do you validate the reality of knowledge which you work with? I.e. Is it in line with how nature actually operates?” My apologies if I’ve misrepresented your question, but if this is what you meant, I would agree that it is a very important question. Unfortunately, it is the most difficult thing to do in practice.

 

I try to be aware of the assumptions I’m making, and to ensure that my conclusions follow logically from those assumptions. I also try to make sure that those assumptions (e.g. causality) accord with reality. However, whether my conclusions correspond to reality is another question. I’ve already admitted that it is not, at present, provable.

 

My thanks for your input.

 

What does this quote have to do with time travel? What is time travel?

 

Hi Atheist. Sorry if I’m “teaching grandmothers to suck eggs”, but the reference to time travel is relevant because General Relativity is partially based on Minkowski’s idea that time is just one of the four dimensions of spacetime. Thus “all imaginable systems of coordinates” includes those which may be in arbitrary motion in the time dimension. This unavoidably requires time travel to be theoretically possible (even if it is not feasible).

 

For an example of what I mean by time travel, please see the reply to insane_alien. I think this is a good example because I have avoided the obvious paradoxes of time travel (killing your own grandmother etc…) and focussed instead on the conclusion that time travel unavoidably implies that the same molecules and atoms can be in two (or more) places at the same time. Travel in the spatial dimensions does not require this. Thus time travel is not equivalent to spatial travel. You can equate them mathematically, but IMHO to suggest that has any relevance to reality is specious.

 

I hope this helps…

[insane_alien]

okay, dude, when relativity says time is just a dimension of space-time it does NOT mean that objects can arbitrarily jump around the timeline like in some cheesy 60's scifi movie. it also does not say that we have any freedom of movement at all in the time dimension.

 

what it does say, is that we are moving along the time axis at some speed that is limited by c and is subject to length contraction. meaning, thefaster you go in the spacial dimensions, the slower you progress through time(outside observers will see your clocks going slow)

 

i think you have a major misunderstanding of relativity and are using the popularised view of time travel most often depicted in movies and such with what a scientist would reffer to as time travel.

 

so i'll define them here for you in general terms

 

movie time-travel: jumping to arbitrary point in time and space from a different arbitrary point in time and space(may be accompanied by a swirly tunnel full of clocks)

scientific time-travel: the rate at which time is passing. so, you are time-travelling just now with a rate of 1 second per second. that is if you take the refference second to be from your frame.to an observer going by at 0.9c then you would be going at 0.5(or there abouts) seconds per second wrt the observer.

[jedaisoul]

okay, dude, when relativity says time is just a dimension of space-time it does NOT mean that objects can arbitrarily jump around the timeline like in some cheesy 60's scifi movie. it also does not say that we have any freedom of movement at all in the time dimension…

 

i think you have a major misunderstanding of relativity and are using the popularised view of time travel most often depicted in movies and such with what a scientist would refer to as time travel.

 

I would not consider Einstein’s 1916 paper to be a “popularised view”. Einstein said “all imaginable systems of co-ordinates”, and I take it that he meant precisely that. All imaginable systems of co-ordinates in a Minkowski spacetime continuum explicitly includes travel in time. Now it may not include jumping around in time, and I'd apologise for using that as an example. But it does include the freedom to move forwards and backwards through time in the manner of H G Wells' time machine.

 

Now that (as we seem to agree) is silly. You may prefer to disown it, but Einstein defined general co-variance and that is what he said it meant.

[insane_alien]

but you can't go back in time. nowhere does it allow that(that would also violate several other laws that also have to be obeyed). but you can change the rate at which you move through time. no one would contend this as we have seen it happen experimentally. and it does not violate causality. there is nothing silly about it it if you look at what is actually allowed and what would require impossible conditions to be allowed.

[jedaisoul]

but you can't go back in time. nowhere does it allow that(that would also violate several other laws that also have to be obeyed). but you can change the rate at which you move through time. no one would contend this as we have seen it happen experimentally. and it does not violate causality. there is nothing silly about it it if you look at what is actually allowed and what would require impossible conditions to be allowed.

 

I'm glad that we agree that it is not possible to go back in time. That would violate causality, as your actions in the past would be predicated on actions that were yet to happen (and may not happen). My problem is not with the modern application of GR, it's with the conceptual framework. As I understand it, and as I've quoted it, general co-variance is fundamental to GR, and it conceptually includes the ability to move as freely in time as we can in space.

 

So although we agree that this is not possible in practice, to me, a conceptual framework that is based on the feasibility of time travel (in that sense) is not a description of reality. Simply agreeing that it cannot happen in practice does not fix the conceptual framework that, in principle, allows it. The conceptual framework of GR does not match reality in this respect.

 

I would stress that this has little or no bearing on the practical application of GR. What I'm saying is that we need to be aware of the limitations of GR as a description of reality. That is why I feel that there is room for the discussion of other speculative models. And that is what I'd rather be doing. This is really just a diversion from the purpose of this thread, to discuss a speculative framework for cosmology that takes Newtonian relativity (with it's acknowledged limitations) and gives it a novel twist.

 

I hope that this clarifies my intentions, and the purpose of this thread.

[timo]

I still only half-ways understand what you are trying to say (specifically, I still don't understand what you call "time travel" - copies of you appearing from nowhere?).

It somehow sounds to me as if you were saying that a coordinate transformation t -> -t would switch past and future. This way of thinking seems to implicitely assume that future and past were defined as t>0 and t<0. Such a definition would not not be invariant under arbitrary coordinate transformations and, as I think you are trying to show, cause problems.

If you define future- and past-lightcone in an invariant way, then future- and past-lightcone will remain unchanged under coordinate transformations.

 

EDIT: I should probably state that I have not read and will not read your original post #1 (because it met the criteria for my "don't bother reading"-quickfilter). What I say is only in reply to the passage quoted in post #5, your reply and your posts #8 and #10). Thus, if what I say is redundant feel free to ignore it (or use the report post function to ask a moderator to remove this post).

[jedaisoul]

I still only half-ways understand what you are trying to say (specifically, I still don't understand what you call "time travel" - copies of you appearing from nowhere?).

It somehow sounds to me as if you were saying that a coordinate transformation t -> -t would switch past and future. This way of thinking seems to implicitely assume that future and past were defined as t>0 and t<0. Such a definition would not not be invariant under arbitrary coordinate transformations and, as I think you are trying to show, cause problems.

If you define future- and past-lightcone in an invariant way, then future- and past-lightcone will remain unchanged under coordinate transformations.

 

Hi Atheist,

 

Please see the comments by insane_alien. He has correctly pointed out that jumping around in time (in the manner of my example) is not supported by GR. I have acknowledged that and apologised. It is a bad example.

 

However, I still maintain that general co-variance, which is fundamental to GR, conceptually allows the freedom of movement forwards and backwards through time. So, in my example, if you assume that the subject is accelerating forwards and backwards in time (rather than making instantaneous movements to and from different times) you arrive at the same conclusion that, in principle, this requires the same atoms and molecules to be in two (or more) places at the same time. This does not arise with movement in space, so movement in space and time are not equivalent.

 

The film “The Time Machine”, which is based on a book by H. G. Wells, uses this form of time travel.

 

However, I should stress that insane_alien interprets time travel (according to GR) differently. He says that GR only allows you to travel forwards in time at different rates. It is this form of time travel that he refers to.

 

Anyway, the question of time travel is incidental to this thread, because my scenario, based on Newtonian Relativity, does not allow any form of time travel. What is does allow is for different passages of time to appear to arise when viewing distant objects.

 

I hope that helps…

[timo]

An explicit (calculational) example for the statement "general covariance allows the freedom of movement forwards and backwards in time" would probably help (same goes for "accelerating forwards and backwards in time"). Particles, by relativity definition, have a path in spacetime with timelike tangent. In non-curved spacetime, this fixes the space position to exactly one position for each time position - regardless of coordinate system (except for time-coordinate being time-like and space-coordinates being space-like).

[jedaisoul]

An explicit (calculational) example for the statement "general covariance allows the freedom of movement forwards and backwards in time" would probably help (same goes for "accelerating forwards and backwards in time"). Particles, by relativity definition, have a path in spacetime with timelike tangent. In non-curved spacetime, this fixes the space position to exactly one position for each time position - regardless of coordinate system (except for time-coordinate being time-like and space-coordinates being space-like).

 

Hi Atheist,

 

Perhaps insane_alien can asist with the mathematics. I'm pimarily interested in the conceptual framework that underlies GR, and whether it corresponds to reality. As I've said, the question is not relevant to my scenario.

[insane_alien]

However, I should stress that insane_alien interprets time travel (according to GR) differently. He says that GR only allows you to travel forwards in time at different rates. It is this form of time travel that he refers to.

 

actually, i just said that you can only go in one direction(your origional direction) at different rates. or at least implied that anyway. anti-matter can be envisioned as normal matter travelling backwards in time(scientificly, not popularized travel in time).

 

what athiest said about the lightcones is what reality behaves like.

[jedaisoul]

actually, i just said that you can only go in one direction(your origional direction) at different rates. or at least implied that anyway. anti-matter can be envisioned as normal matter travelling backwards in time(scientificly, not popularized travel in time).

 

what athiest said about the lightcones is what reality behaves like.

 

Thank you for clarifying. I had no intention to mis-quote you.

[insane_alien]

don't worry i'm just making sure everyone keeps the facts straight as things get ultrapointless ultrafast when the get twisted whether it is intentional or not.